Controller for electric motors



; 1643127 Sept. 20, 1927. N L. MORTENSEN r CONTROLLER FOR ELECTRIC MQKI'ORS Filed April 25. 1921" 3.. 4 m v M u m J v L U u v g M. a G 0 o m P k ,fl mN u 1 INVENITOR.

' TTORNEY Patented Se t. 20, 1927.

UNITED STATES PAreT orrce.

NIEL S L. MORTENSEN, OF MILWAUKEE, WISCONSIN, ASSIGNOR TO THE CUTLERT-HAM- MEB MFG. (30., OF MILWAUKEE, WISCONSIN, A CORPORATION OF WISCONSIlIN.

CONTROLLER ron ELECTRIC morons.

Application filed April 25, 1921.

This invention relates to controllers for electric motors and more particularly to dynamic braking controllers for motors employed in driving bucket hoists and the like.

In the operation of such hoists 1t 15 customary to apply dynamic braking to the driving motor for lowering of the bucket. It is also customary in certain classes of hoists to employ in addition to the hoisting line and drum a further line and drum for effecting holding of the bucket to permit slacking of the hoisting line for opening of the bucket and where such drums are employed it is common practice to employ a sinr gle motor geared directly to the hoisting drum and to employ a clutch or other releasable power connection between the motor and the holding drum.

In an installation such as that just described, closure of the bucket is efi'ected by operating the motor to drive the hoisting drum in a direction to wind up its associated line, the clutch being released thus rendering the holding drum idle. For hoistlng, the clutch is engaged and the motor operated for causing both drums to draw in their respective lines. Opening of the bucket is efiected by release of the clutch and applying a positive braking act-ion to the holding drum, the motor being reconnected to its supply line in a manner such that the supplied current divides between the field and armature of the motor and traverses portions of the dynamic braking loop aforementioned, the field being in effect connected in shunt to thearmature and the direction of current through the armature being relatively reversed, thus effecting revers operation of the motor for slacking off the hoisting line, the bucket being thereupon adapted to open under theforce ofgravity. For lowering, the circuit connections last described are maintained, the clutch, however, being engaged and the brake released. For stopping or holding, the

clutch is maintained engaged thus connecting both 'drums to the motor whereas the latter is disconnected from its supply lines,

' its field and armature, however, being connected in a closed loop including suitable resistance to provide for dynamic braking when the motor revolges in the lowering direction. v

While the aforedescribed control of the motor is reasonably adequate for effecting Serial No. 464,410..

operation of certain types of bucket wherein the entire weight of the bucket-and contents tends to effect opening thereof, nevertheless, in other types of bucket wherein less than the total weight of the aforementioned parts is utilized for such purpo. or in general where a rapid opening 0 the bucket is desired the same cannot be efiected by such system of control without drawing currentfrom the supply line considerably in excess of that required for hoisting purposes whereas even if such heavy current consumption be permitted the time required for opening of the bucket may still be disproportionately long.

The present invention has among its ob jects that of reducing the time required to effect opening of the bucket assuming a predetermined current consumption rate or conversely for reducing the current consumption rate required to efiect opening of the bucket 1n a given time. 4

A further object is that of so reducing either the time or the current required to effect opening of the bucket, or both, while maintaining the latter at all times subject to application of a relatively high degree of dynamic braking action in the event of failure of the voltage of the supply line.

Other objects and advantages will hereinafter appear.

The accompanying drawing, consisting of a single figure, illustrates diagrammatically and schematically a controller adapted to provide the foregoing features.

As illustratedin the drawing and more fully described hereinafter, the circuit connections effected are such that during reverse operation of the motor for opening of the bucket the motor field and armature are arranged in series relation, rather than in shunt relation as in controllers heretofore proposed, whereby practically the total value whereby either the time or the current required to efl'ect'opening .of the" bucket, or both, may be materially reduced.

Referring to the drawing the same illustrates a hoisting motor, havin an armature 5 and series field 6, to be supplied with direct current from lines L, L and provided with 40 line L 50 the motor serves to drive "hoisting thexclosed bucket.

55 R and that is to say, to

accelerating resistance R, R. A closing line 7 is coiled about a suitable drum 8, the latter having a positive power connection with said motor whereas a hoisting and holding line 9 is coiled about a suitable drum 10, the

latter being operatively connected to the motor through a releasable clutch 11. A. conventional form of brake 12 is provided for said latter-mentioned drum.

Control of the motor is effected by means of electro-responsive switches 13 to 21, the action of the latter being subjected to voluntary control by means of a drum controller ,22 and a further manual switch 23 amo 15 ciated therewith, certain of said electro-responsive switches being provided with electrical or mechanical interlocks for effecting automatic control features to be described. 1 Moreover, switches 16 and 17 are of the nor- 20 .mally closed type being'biased by gravity,

s rin pressure or otherwise, to assume c ose position unless positlvely held open due to energizatlon of their respective wind- 1n s.

n practice the switch 23 is preferably arranged to be operated by means of a button, grip device or the like associated with the usual drum operating handle although obviously said switch may be arranged for operation in any desired or preferred manner.

The operation ofthe device maybe described as follows. Assuming the bucket to be lowered and 0 en, the clutch disenga ed, the brake release 6 by conductor 28 throng? accelerating re- 45 sistance sections=R and 2 and by conductor 29 through switch 21 to line L The motor thereupon operates the drum 8 for clo- 'sure of the bucket and following such action the clutch 11 is caused to on age whereupon 0th drums for Furt er movement of the drum controller to the right serves to efiect progressive shortcircuitin of, accelerating resistance sections 2 through the closure of accelerating switches 18 and 19, the latter being electrically interlocked as illustrated to insure proper sequence of closure thereof.

Return movement of the drum controller ition serves to restore the various contro switches to their positions illustrated, rmit o nin of switches 14 and 21 and'c osure'o' switc terminal.

allel' to one another and-are re and the various contro ler- 35 parts in the positions illustrated, movement 17. Suchri j agtion obviously disconnects the motor from the supply circuit andlconnect s the armature and field thereof in a closed loopincluding a suitable resistance step R Said loop may be traced from the left hand armature terminal by conductor}; 25 and 30 to and through resistance R thence by conductor 31 through switch 17 by conductors 32 and 28 through the series field 6'and through switch 16 to the opposite armature Obviously due to such connection the overhauling load of the bucket causes the motor to act as a generator with respect to the aforedcscribed' loop, the resistance of which is relatively low whereby the, motor serves to limit the rate of descent of the load to a relatively small value. I

For lowering the bucket, the drum controller ismoved to the left and in its first on position serves to effect closure of switches 13, 18, 19, 20 and 21 with opening of switch 17. Such commutation serves to include acceleration resistance sections 3', R in the aforedescribed dynamic loop, subject, however, to reopening of switches 18 and 19, and also serves to effect line connection of the motor such that, as regards such connection, the armature and field are arranged in paratively 'reversed.

\Vith reference to such line connection, the

armature circuit 'now extends from line L by conductors 24 and 33 through switch 13 and through current limiting resistance R, thence by conductors 34 and 26 through the armature in a reverse direction, by conductors 25 and 30 through resistance R, thence by conductor 35 through switch 20 and by conductors 36 and 29 through switch 21 to line L The field circuitv also extends from line L through switch 13 to conductor 26 as formerly traced, the current dividing at the junction of conductors 34 and 26 and the field current passing through switch 16,

thence through the field in the same direction as formerly, thence through accelerating switches 18 and 19 and through switch 21 to line L.

Further movement of the'drum controller to the left to successive positions. serves to include rogressivel Y the resistance sections R and 1 in the eld. circuit due to progressive opening of switches 19 and 18, thus effecting acceleration of thelowering act-ion due to weakening of the field.

To effect opening of the bucket the drum controller is returned to its first lowering position thus picking up switches 18 and 19 rogressively, the remaining switchesxbeing in their positions last described. Under such conditions the manual switch 23 is closed thus effecting o ening of switch 16 and closure of s'witc 15, said switches being rovid'ed with interlocks as illustrated for insuring opening of switch 16 prior to closure of switch 15 'Closureof said switch also serves through opening of its auxiliary contacts to effect de-energization and opening of the switch 20.

The motor circuit as thus commutated is as follows, namely, from line L by way of switch 13 to the right hand armature terminal as formerly traced thence through the armature by conductors 25, and 37 through switch 15 thence by conductors 38,

ing connected in series and hence traversed by the full input current, subject, however, to the action of an armature shunt hereinafter described, whereby a high speed of the motor is provided for rapid reverse rotation of the drum 8 and resulting in very expeditious opening of the bucket, it being understood that under these conditions the clutch 11 is released and the drum 10 subjected to braking action for preventing lowering of the bucket as a whole.

The commutations last described further serve to provide a path for the field current through resistance R and in shunt with the armature, thereby insuring sufficient field excitation to check the speed of the motor under the overhauling load upon line 7 following acceleration of drum 8. V

The. aforedescribed construction and arrangement additionally provide full pro tection against droppin of the bucket due to failure of voltage 0 the supply circuit, the aforementioned rapid reverse operation of the motor being dependent upon maintenance of the switches 16 and 17 in open position, said switches, moreover, being biased to close and being held open only by means of their electro-magnetic windings. Thus should the voltage across the supply circuit fail, all of the magnetically closed switches will at once open and the magnetically opened switches will immediately close.

Such action serves to short-circuit the motor upon itself through the resistance section B whereby the load will be constrained to descend gradually, precisely as occurs when the drum controller moves to off position.

In practice it has been found possible by means of the special features aforedescribed to reduce the current required to open the bucket to 75% of that required for hoisting, the time required for opening the bucket being not increased over that required by the use of the ordinary dynamic lowering controller which may require as high as 150% of the hoisting current to effect opening of the bucket in such time.

Since the torque as well as thespeed of.

the motor is materially increased due to the 'f'a foredescribed full reverse connections of the motor, the device is equally well adapted to use in hoists wherein a counterweight must be lifted in order to effect opening of the bucket. Further the special control herein contemplatedis applicable with equal advantage to systems wherein the closing l ne and the combined hoisting and holding line are operated by individual motors, or in fact to any of the usual types of dynamic lowering hoisting controllers.

What I claim as new and desire to secure by Letters Patent is:

1. The combination with a reversible driving motor for bucket hoists and the like,'of 1 control means therefor comprising a drum movable to effect series connection of the motor field and armature to the line for hoisting and also movable to effect parallel connection of said elements to the line in reyerse relation to each other for lowering, independently operable means associated with said former means for alternatively'effecting se ies connection of said elements in motor field and armature in a given relation for hoisting, means to effect parallel connection of said elements with'respect to the l1Ile\ for lowering, independently operable means associated with said former means for effecting series connection of said elements in a lowering relation to thereby provide for rapid opening of the bucket, and means to insure dynamic braking connections for the motor upon movement of said drum to ofi position or upon failure of line voltage.

3. In a controller for bucket hoists and o the like, the combination with a reversible driving motor, of a plurality of electro-responsive switches for commutation of the motor circuit, including switches adapted when de-energized to establish a dynamic braking loop for the motor, of means for controlling the action of the switches to provide for effecting line connection of the motor field and armature in a given relation for hoist-ing and for effecting line connection of said loop to provide parallel connection of the motor elements in reverse relation to one another for lowering, and independently operable means to provide for line connection of said elements in series in sa-id'latter relation for rapid opening of the bucket.

4. In a controller for bucket hoists and the like, the-combination with adriving motor, of a plurality of electro-responsive switches for commutation of the motor circuit, including switches adapted when deenergized to establish a dynamic braking loop for the motor, of a drum controller governin the energization of the switches to provi e for effecting line connection of the motor field and armature in a given relation for hoisting and line connections for such loop to parallel the motor elements in reverse relation for lowering, and an independently operable switch adapted, followmg a given positioning'of said drum controller, to provide for line connection of said motor elements in series in said reverse relationto one another for rapidopening of the bucket.

5. In a controller for bucket hoists and the like, the combination with a driving motor,-of a plurality of electro-responsive switches for commutation of the motor circuit, including switches adapted when deenergized to establish a dynamic braking loop for'the motor, of a drum controller for the switches operable in one direction from off position to effect line connection of the motor field and armature in a given relation for hoisting and also operable in a reverse direction from off position to provide line connections for such loop to effect parallel connection of the motor elements in reverse relation for lowering, and a separately operable switch associated with the operating handle of said drum controller and biased to inoperative position and operable following positioning of the drum controller in lowering relation to effect line connection of said motor elements in series in said reverse relation to bucket. v

6. In a controller for bucket hoists and the like, the combination with bucket holding and closing lines, a drum for each of said lines, a driving motor and releasable clutchmechanism providing for joint operation of said drums or individual operation of one of said drums, a brake for the other of said drums, and control means for the motor comprising a drum controller to effect series connection of the motor field and armature in a given relation for'hoisting and to effect parallel connection of the gnor field and armature in reverse relation one another for lowering, independently operable commutating means associated with said drum controller to effect series connection of said field and armature -in said reverse relation, said clutch being released and said brake applied, and means for insuring dynamic brakingconnections for the motor upon failure of line voltage or upon movement of said drum controller to off position.

In witness whereof, I have hereunto subscribed my name.

, NIELS L. MORTENSEN.

provide for rapid opening of the 1 

